Suppression of 1,2-diaminocyclohexane formation during production of hexamethylenediamine

ABSTRACT

In the process of preparing hexamethylenediamine by the catalytic hydrogenation of adiponitrile in the presence of ammonia contacting the adiponitrile during hydrogenation with a compound selected from the group consisting of RCOM, where R is selected from the group consisting of hydrogen and an alkyl radical having from 1 to 3 carbon atoms and M is selected from the group consisting of the radicals OH, NH2, ONH4, ONa and OR&#39;&#39; where R&#39;&#39; is selected from the group consisting of alkyl radicals having from 1 to 3 carbon atoms, glyoxal and carbon monoxide.

'United States Patent [191 Williams et a1.

[ NOV. 4, 1975 [75] Inventors: John Ronald Williams, Victoria,

Tex.; Terry Gene Lenz, Fort Collins, C010.

[73] Assignee: E. I. Du Pont de Nemours &

Company, Wilmington, Del.

[22] Filed: July 31, 1974 [21] Appl. No.: 493,743

[52] US. Cl 260/583 K; 260/563 D; 260/583 P;

[51] Int. Cl. C07C 87/14 [58] Field of Search 260/583 K, 583 P, 563 D,260/583 M [56] References Cited UNITED STATES PATENTS 3,061,644 10/1962Fierce et a1. 260/583 K 3,117,162 1/1964 Rylander et a1 260/583 K3,152,184 10/1964 Levering et 211.

3,235,600 2/1966 Evans 260/583 K 3,773,834 11/1973 Bivens et a1 260/583K Primary ExaminerArthur P. Demers [5 7] ABSTRACT In the process ofpreparing hexamethylenediamine by the catalytic hydrogenation ofadiponitrile in the pres ence of ammonia contacting the adiponitrileduring hydrogenation with a compound selected from the group consistingof RCOM, where R is selected from the group consisting of hydrogen andan alkyl radical having from 1 to 3 carbon atoms and M is selected fromthe group consisting of the radicals OH, NH ONH ONa andOR' where R isselected from the group consisting of alkyl radicals having from' 1 to 3carbon atoms, glyoxal and carbon monoxide.

10 Claims, N0 Drawings SUPPRESSION OF 1,2-DIAIVHNOCYCLOHEXANE FORMATIONDURING PRODUCTION OF HEXAMETHYLENEDIAMINE BACKGROUND OF THE INVENTIONThe process of the present invention relates to the preparation ofhexamethylenediamine. More specifically, the present invention relatesto the reduction of the impurity, 1,2-diaminocyclohexane, inhexamethylenediamine produced by the catalytic hydrogenation ofadiponitrile.

PRIOR ART The preparation of hexamethylenediamine (HMD) by the catalytichydrogenation of adiponitrile (ADN) in the presence of ammonia is knownin the art. One such method is US. Pat. No. 3,471,563.

In the manufacture of hexamethylenediamine by the catalytichydrogenation of adiponitrile several by-products are produced. One ofthe by-products produced which is the most difficult to separatefrom-the crude hexamethylenediamine is 1,2-diaminocyc'ilohexane. Theboiling point of l,2-diaminocyclohexane is close enough tohexamethylenediamine to present a difficult problem to the purificationof hexamethylenediamine by fractional distillation. Additionally thedistillation equipment required to remove 1,2-diaminocyclohexane fromcrude hexamethylenediamine is extremely costly to operate. Such adistillation step results in losses of hexamethylenediamine andconstitutes a bottleneck in the refining operation and overallproduction of hexamethylenediamine. The presence of 1,2-diaminocyclohexane (DCH) in the hexamethylenediamine at the normal levelhas a deleterious effect on the properties of the nylon producedtherefrom. The presence of 1,2-diaminocyclohexane in the production ofpolyhexamethylene adipamide results in a lower molecular weight polymerhaving irregular tensile strength, poor color characteristics, poordyeability and other inferior chemical and physical properties.

Hexamethylenediamine can be produced by a number of methods. However,none of these methods result in the production of hexamethylenediaminewhich is free from products of side reactions. One process used toproduce hexamethylenediamine (HMD) is described in US. Pat. No.3,471,563. However, the process for preparing HMD by the catalytichydrogenation of adiponitrile in the presence of ammonia is well knownin the art.

In US. Pat. No. 3,235,600 the DCH content of HMD is reduced by the useof inorganic or organic carbonates, organic and inorganic carbamates andcarbon dioxide. The present invention involves additives that suppressDCH in HMD or reduce DCH and do not involve carbon dioxide or the abovecarbonates or carbamates.

Summary of the Invention Now it has been found that the level of 1,2-diaminocyclohexane in hexamethylenediamine produced by the catalytichydrogenation of adiponitrile can be reduced by use of the additivecompounds of the present invention. Thus according to the presentinvention the impurity level of 1,2-diaminocyclohexane inhexamethylenediamine produced by the catalytic hydrogenation ofadiponitrile was reduced by contacting the adiponitrile with a compoundselected from the 2 group consisting of RCOM, where R is selected fromthe group consisting of hydrogen and an alkyl radical having from 1 to 3carbon atoms and M is selected from the group consisting of the radicalsOH, NH ONH 5 ONa and OR where R is selected from the group consisting ofalkyl radicals having from 1 to 3 carbon atoms, glyoxal and carbonmonoxide, wherein the mol percent of the RCOM and glyoxal is from 0.2 to2.4, preferably 0.50 to 1.50, and the carbon monoxide is from 0.075 to0.150, preferably 0.100 to 0.140 based on the adiponitrile.

The use of the additives of the present invention does not substantiallyaffect the activity or rate of hydrogenation and in the case of thepreferred RCOM type additives the rate appears to be unchanged orimproved.

Thus in accordance with the invention adiponitrile, ammonia and hydrogentogether with an additive compound of the present invention are passedover or through a hydrogenation catalyst under hydrogenationtemperatures and pressures thereby forming crude hexamethylenediaminethat contains reduced quantities of 1,2-diaminocyclohexane.

The hydrogenation temperature for the process of the present inventionmay be between 25C. and 210C. and the hydrogenation pressure may bemaintained between 25 and 10,000 pounds per square inch or higher withthe preferred temperature being in the range of C. to' C. and thepreferred pressure being in the range of 4,000 to 6,000 psig. In thepractice of the invention it is preferred generally to carry out thehydrogenation at the lowest temperature and hydrogen pressure at whichhydrogen is absorbed at a reasonably rapid rate.

The hydrogenation of adiponitrile to hexamethylenediamine may beaccomplished by the use of various hydrogenation catalysts.Representative examples of such catalysts include nickel, cobalt,copper, zinc, platinum, palladium, iron, rubidium, ruthenium, Raneycatalysts and the like. The hydrogenation catalysts may be in the formof free metalspr in the form of compounds such as oxides or salts: Thehydrogenation catalysts may be employed in conjunction with knownpromoters and/or supports. I

These above mentioned catalytic materials are used preferably in afinely divided form and may be deposited on a porous supporting meanssuch as pumice, kieselguhr, alumina gel and silica gel. Catalyst powdersare prepared conveniently for use in the hydrogenation process bycompressing the catalyst into pellets or brickets of suitable size.Stabilized catalysts containing a substantial proportion of oxide,catalysts comprising the carbonate, oxide or hydroxide of thehydrogenating metal deposited on an inert porous support, and catalystsin which the hydrogenating metal is combined with a nonreducible oxideare preferably reduced in a stream of hydrogen-containing gas prior toexposure to the reaction compounds.

The additive compounds of the present invention may be selected fromRCOM, glyoxal and carbon monoxide where R in the formula RCOM ishydrogen or alkyl of l to 3 carbon atoms and M is OH, NH ONH ONa or ORwhere R is an alkyl radical of l to 3 carbon atoms. Thus the compoundsrepresented by the formula RCOM may be amides, acids, salts and esters.Representative examples of RCOM compounds include methyl formate, ethylformate, propyl formate, formamide, formic acid, ammonium formate,sodium formate, acetic acid, acetamide, ammonium acetate,

sodium acetate, methyl acetate, ethyl acetate, propyl acetate, propionicacid, propionamide, ammonium propionate, sodium propionate, methylpropionate, ethyl propionate, propylpropionate, butyric acid,butyramide, ammonium butyrate, sodium butyrate, methyl butyrate, ethylbutyrate, propyl butyrate, and the like.

The additive compounds of the present invention which suppress theformation of 1,2-diaminocyclohexane (DCH) present inhexamethylenediamine (HMD) produced by the catalytic hydrogenation ofadiponitrile (ADN) in the presence of ammonia may be selected fromcompounds of the general formula ROM (where R and M are as definedabove), glyoxal and carbon monoxide. The amounts of the additives mayvary somewhat depending on the additive selected. When carbon monoxideis used as the amount used approaches or goes beyond 0.150 mol percentthe reduc tion of DCl-l tends to be overshadowed by the reduction inrate due to poisoning of the catalyst. Thus greater amounts of carbonmonoxide will further reduce the DCH content of the crude HMD. Among thepreferred compounds represented by the above formula RCOM, the mostpreferred is formamide. The preferred compounds of the presentinvention, those represented by the formula RCOM as defined above, notonly reduce the DCH content of the HMD but also either result in animproved rate or no rate reduction when compared to no additive beingused.

The weight ratio of liquid ammonia to adiponitrile in the process ofpreparing adiponitrile may be from 1:1 to :1; however, greater amountsof ammonia relative to adiponitrile can be used but practically are notdesirable for the reason that separation problems arise with greaterlevels of ammonia. The preferred level of ammonia to adiponitrile is 4:1.

The following examples are provided to further illustrate the presentinvention. The weight percent and mol percent of the additives of thepresent invention are based on the adiponitrile used.

The activity of the hydrogenation catalyst in the following examples wasthe rate at which it promotes the hydrogenation of adiponitrile tohexamethylenediamine. This rate of hydrogenation was monitored bymeasuring the amount of hydrogen used per unit time during the reaction.The amount of hydrogen used was determined by continuously recording thepressure of a fixed volume of hydrogen feed gas. The effect of variousadditives were thus compared to each other at a relative basis ofhydrogen usage in gram moles of hydrogen per minute per gram ofcatalyst. The runs were terminated when the hydrogen usage was very slowor after a 1,400 or 1,500 psig pressure reduction in the feed tankoccurred.

EXAMPLE 1 1n a dry nitrogen atmosphere 70.0 grams of adiponiwas added35.0 grams of reduced iron catalyst, according to the teaching of US.Pat. No. 3,696,153. The ADN and catalyst were transferred to an Amincohighpressure rocking reactor having a volume of 1.15 liters. The reactorwas then sealed and evacuated. To the ADN-catalyst mixture was thenadded 280 grams of anhydrous ammonia by forcing-it into the rockingassembly using 300 psi hydrogen. The mixture was agitated by a rockingmotion while the reactor was heated to 150C. The hydrogenation ofadiponitrile to hexamethylenediamine was initiated by pressurizing thereactor with hydrogen to 5,000 psig and maintaining the pressure at5,000 psig during the entire reaction period. The extent and rate ofhydrogenation was determined by measuring the hydrogen fed to thereaction from a feed tank initially at 8,000 psig using the appropriatecorrections for temperature and compressibility of hydrogen. Thereaction temperature was maintained at 150 2C. during the two-hourreaction time. The reaction was considered to be complete when nohydrogen was used for approximately 10 minutes. After cooling to 135C.the rocking motion was stopped and the excess hydrogen and ammonia werevented and the pressure reduced to one atmosphere. The activity or ratewas 1.15. The entire sample of this crude hexamethylenediamine productwas removed from the reactor. Laboratory analysis using a calibrated gaschromatograph showed 0.33% 1,2-diaminocyclohexane in the crudehexamethylenediamine product.

EXAMPLE 2 The procedure of example 1 was followed except that a newreaction mixture was prepared by adding 0.53% by weight or 0.37 grams ofglacial acetic acid (0.95 mol to grams of adiponitrile prior to itsbeing mixed with the liquid anhydrous ammonia. Analysis of the crudehexamethylenediamine produced showed 0.20 weight percent1,2-diaminocyclohexane in the crude hexamethylenediamine product or a39.4% reduction in the 1,2-diaminocyclohexane produced in example 1.

EXAMPLE 3 Following the procedure and amounts of example 1 the amount of1,2-diaminocyc1ohexane present in the hexamethylenediamine (l-llVlD) wasdetermined as a control. HMD was prepared using the portion indicated inexample 1 of the same ADN and catalyst by the procedure shown in example1 except that 0.38% by weight (0.89 mol by weight of formic acid wasadded to the adiponitrile as the l,2-diaminocyclohexane suppressant andlaboratory analysis of the crude hexamethylenediamine produced showed0.21 weight percent 1,2-diaminocyc1ohexane or a 45% reduction in the1,2-diaminocyc1ohexane produced without the formic acid. The activity orrate was 1.43 as compared to 1.15 without formic acid. A repeat of thisrun and control yielded the results given in Table 1 under the sameconditions except as indicated.

TABLE l-continued Catalyst Temp. Formic Acid Activity" DCH PercentReduction (grams) (C) (Wt (M0170) or Rate, Wt in DCH gram-mole ofhydrogen used *Rate X 10 mlnutes, grams of catalyst EXAMPLE 4 EXAMPLES6i0 Following the procedure and amounts of example 1, the amount of1,2-diaminocyclohexane present in the hexarnethylenediamine (HMD) wasdetermined as a control. HMD was prepared using the portion indicated inexample 1 of the same ADN catalyst by the procedure shown in example 1except that 0.30 weight percent (0.56 mol glyoxal was added to theadiponitrile v Following the procedure and amounts recited in example lthe amount of 1,2-diaminocyclohexane present in HMD was determined as acontrol. HMD was prepared using the procedure and portions indicated inexample 1 of the same ADN and catalyst but using the amount of methylformate indicated below in Table ll.

TABLE II.

LZ-Diaminocyclohexune Reduction in 1.2-. I Methyl Formutc in Crude HMDActivity Diaminocyclohexane Ex. (Wt%) (M61% (Wt 72) 01' Rate (71) 6 0 00.63 1.34. 7 0.36 0.66 0.42 1.28 33.3 8 0.57 1.04 0.41 1.49 34.9 9 0.791.44 0.32 1.27 49.2 10 0.93 1.74 0.31 1.31 50.8

as the LZ-diaminocyclohexane suppressant. Labora- Beyond about 1.44 molpercent the percent reductory analysis of the crudehexamethyl'enediamine prodtion in DCH did not significantly change. uctshowed 0.23 weight percent l,2-diaminocyclohexane or a reduction in the1,2-diaminocyclohexane v d EXAMPLES I 147 produced without glyoxal. Theactivity or rate was 1.59 The procedure and amounts recited in example 1as compared to 1.62 without glyoxal. were usedand the amount of1,2-diaminocyclohexane present in the HMD produced was determined as aEXAMPLE 5 control. Using the same ADN and catalyst HMD was Following theprocedure and amounts of example 1 produced with the additive andamounts shown below the amount of l,2-diaminocyclohexanepresent in thein Table Ill.

TABLE III 1,2-Diaminocyclohexane Reduction in L2- Formamide in Crude HMDActivity Diaminocyclohexane Ex. (Wt 70) (Mel (Wt or Rate At mol percentof formamide beyond about 1.46 the percent reduction of DCH was eithernonsignificant or hexamethylenediamine (HMD) was determined as aunchanged. control. HMD was prepared using the portion indicated inexample 1 of the same ADN and catalyst by the pro- EXAMPLES 17-25 cedureof example 1 except that 0.44 weight percent The procedures and amountsrecited in example 1 (0.75 mol ammonium formate was added to the adiwereused and the amount of 1,2-diaminocyclohexane ponitrile as the1,2-diaminocyclohexane suppressant. present in the HMD produced wasdetennined as a Laboratory analysis of the crude hexamethylenedicontrol.Using the same ADN and catalyst HMD was amine product showed 0.20 weightpercent 1,2- produced with the additive of carbon monoxide. Thediaminocyclohexane which amounts to a 47.4% reduccarbon monoxide wasadded to the ADN in the reaction over the control without ammoniumformate. The activity or rate was L93 as compared to 1.37 withoutammonium formate.

tion and then followed by the ammonia addition indicated to push all ofthe carbon monoxide into the reactor. Table IV summarizes the data.

TABLE IV Volume of CO 1,2-Diaminocyc1ohexane Reduction in 1,2-

at 1 atmos. Carbon Monoxide in Crude HMD Activity Diaminocyclohexane Ex.(cc) (Wt%) (Mol (Wt 70) or Rate 18 O O O 0.63 1.34 19 3.5 0.006 0.0220.60 1.03 20 7.0 0.01 1 0.044 0.49 1.09 22 21 8.4 0.014 0.053 0.58 1.068 22 9.4 0.015 0.060 0.54 1.15 14 23 11.9 0.020 0.075 0.57 0.83 24 14.00.023 0.089 0.49 1.04 22 25 30.0 0.049 0.190 0.41 0.95 35 The rate ofreaction was reduced from a comparative level of 1.34 without anaddition to 0.95 indicating an attack on the catalyst hy the Carbonmonoxide.

The exact reason for the variation of the DCH levels observed in the useof different batches of catalyst and adiponitrile is not known. Onepossible cause for the DCl-l variation may be related to impurities inthe adiponitrile or to composition or structural changes in the catalystfrom lot to lot.

Hexamethylenediamine is a well known compound that is used to producepolyamides by condensing with dibasic acids.

The present invention presents advantages over previously known methodsof manufacturing hexamethylenediamine (HMD). The HMD of the presentinvention has greatly reduced concentrations of DCH. The HMD producedaccording to the process of the present invention reduces the DCHconcentration from 20 to 50% over that HMD prepared without theadditives of the present invention.

We claim:

1. In the preparation of hexamethylenediamine by the catalytichydrogenation of adiponitrile in the presence of ammonia at atemperature from 25C. to 210C. and a pressure of from 25 to 10,000 psig,the improvement comprising contacting the adiponitrile during saidhydrogenation with a compound selected from the group consisting ofRCOM, where R is selected from hydrogen and alkyl having 1 to 3 carbonatoms and M is selected from the radicals OH, NH

ONH ONa and OR wherein R is selected from alkyl radicals having 1 to 3carbon atoms, glyoxal and carbon monoxide, the mol percent of RCOM andglyoxal being from 0.2 to 2.4 and carbon monoxide being from 0.075 to0.150, based on the adiponitrile, and recovering crudehexamethylenediamine with reduced 1,2- diaminocyclohexane.

2. The process of claim 1 wherein the adiponitrile is contacted withRCOM.

3. The process of claim 1 wherein the adiponitrile is contacted withglyoxal.

4. The process of claim 1 wherein the adiponitrile is contacted withcarbon monoxide.

5. The process of claim 2 wherein RCOM is formamide.

6. The process of claim 1 wherein the amount of RCOM and glyoxal is 0.50to 1.50 mol percent and carbon monoxide is 0.10 to 1.40 based on theadiponitrile.

7. The process of claim 6 wherein the adiponitrile is contacted withRCOM.

8. The process of claim 7 wherein the RCOM is fortnamide.

9. The process of claim 6 wherein the adiponitrile is contacted withglyoxal.

10. The process of claim 6 wherein the adiponitrile is contacted withcarbon monoxide.

1. IN THE PREPARATION OF HEXAMETHYLENEDIAMINE BY THE CATALYTICHYDROGENATION OF ADIPONITRILE IN THE PRESENCE OF AMMONIA AT ATEMPERATURE FROM 25*C. TO 210*C. AND A PRESSURE OF FROM 25 TO 10,000PSIG., THE IMPROVEMENT COMPRISING CONTACTING THE ADIPONITRILE DURINGSAID HYDROGENATION WITH A COMPOUNDD SELECTED FROM THE GROUP CONSISTINGOF RCOM, WHERE R IS SELECTED FROM HYDROGEN AND ALKYL HAVING 1 TO 3CARBON ATOMS AND M IS SELECTED FROM THE RADICALS OH, NH2, ONH4, ONA ANDOR'' WHEREIN R'' IS SELECTED FROM ALKYL RADICALS HAVING 1 TO 3 CARBONATOMS, GLYOXAL AND ARBON MONOXIDE, THE MOL PERCENT OF RCCOM AND GLOXALBEING FROM 0.2 TO 2.4 AND CARBON MONOXIDE BEING FROM 0.075 TO 0.150,BASED ON THE ADIPONITRILE, AND RECOVERING CRUDE HEXAMETHYLENEDIAMINEWITH REDUCED 1.2-DIAMINOCYCLOHEXANE.
 2. The process of claim 1 whereinthe adiponitrile is contacted with RCOM.
 3. The process of claim 1wherein the adiponitrile is contacted with glyoxal.
 4. The process ofclaim 1 wherein the adiponitrile is contacted with carbon monoxide. 5.The process of claim 2 wherein RCOM is formamide.
 6. The process ofclaim 1 wherein the amount of RCOM and glyoxal is 0.50 to 1.50 molpercent and carbon monoxide is 0.10 to 1.40 based on the adiponitrile.7. The process of claim 6 wherein the adiponitrile is contacted withRCOM.
 8. The process of claim 7 wherein the RCOM is formamide.
 9. Theprocess of claim 6 wherein the adiponitrile is contacted with glyoxal.10. The process of claim 6 wherein the adiponitrile is contacted withcarbon monoxide.